//
// RTUPort.cpp
//
// Library: IoT/Modbus
// Package: ModbusMaster
// Module:  RTUPort
//
// Copyright (c) 2015, Applied Informatics Software Engineering GmbH.
// All rights reserved.
//
// SPDX-License-Identifier: GPL-3.0-only
//


#include "RTUPort.h"


namespace IoT {
namespace Modbus {
namespace RTU {


RTUPort::RTUPort(Poco::SharedPtr<Poco::Serial::SerialPort> pSerialPort, Poco::Timespan frameTimeout, ByteOrder byteOrder):
	_pSerialPort(pSerialPort),
	_frameTimeout(frameTimeout),
	_byteOrder(byteOrder),
	_sendBuffer(RTU_MAX_PDU_SIZE),
	_receiveBuffer(RTU_MAX_PDU_SIZE)
{
}


RTUPort::~RTUPort()
{
}


Poco::UInt8 RTUPort::receiveFrame(const Poco::Timespan& timeout)
{
	std::size_t n = 0;
	bool frameComplete = false;
	do
	{
		std::size_t rd = _pSerialPort->read(_receiveBuffer.begin() + n, _receiveBuffer.size() - n, _frameTimeout);
		if (rd == 0) return 0;
		if (rd == 1 && n == 0 && _receiveBuffer[0] == 0)
		{
			// ignore spurious null bytes before frame
			if (poll(timeout))
				continue;
			else
				throw Poco::TimeoutException();
		}
		n += rd;
		frameComplete = checkFrame(n);
	}
	while (!frameComplete && n < _receiveBuffer.size());

	return frameComplete ? _receiveBuffer[1] : 0;
}


void RTUPort::reset()
{
	_pSerialPort->drain();
	Poco::Timespan timeout(_frameTimeout);
	while (_pSerialPort->available() > 0 || _pSerialPort->poll(timeout))
	{
		std::string buffer;
		_pSerialPort->read(buffer);
	}
}


Poco::UInt16 RTUPort::updateCRC16(Poco::UInt16 crc, Poco::UInt8 byte)
{
	static Poco::UInt16 crcTab[] = {
		0x0000, 0xc0c1, 0xc181, 0x0140, 0xc301, 0x03c0, 0x0280, 0xc241, 0xc601, 0x06c0, 0x0780, 0xc741, 0x0500, 0xc5c1, 0xc481, 0x0440,
		0xcc01, 0x0cc0, 0x0d80, 0xcd41, 0x0f00, 0xcfc1, 0xce81, 0x0e40, 0x0a00, 0xcac1, 0xcb81, 0x0b40, 0xc901, 0x09c0, 0x0880, 0xc841,
		0xd801, 0x18c0, 0x1980, 0xd941, 0x1b00, 0xdbc1, 0xda81, 0x1a40, 0x1e00, 0xdec1, 0xdf81, 0x1f40, 0xdd01, 0x1dc0, 0x1c80, 0xdc41,
		0x1400, 0xd4c1, 0xd581, 0x1540, 0xd701, 0x17c0, 0x1680, 0xd641, 0xd201, 0x12c0, 0x1380, 0xd341, 0x1100, 0xd1c1, 0xd081, 0x1040,
		0xf001, 0x30c0, 0x3180, 0xf141, 0x3300, 0xf3c1, 0xf281, 0x3240, 0x3600, 0xf6c1, 0xf781, 0x3740, 0xf501, 0x35c0, 0x3480, 0xf441,
		0x3c00, 0xfcc1, 0xfd81, 0x3d40, 0xff01, 0x3fc0, 0x3e80, 0xfe41, 0xfa01, 0x3ac0, 0x3b80, 0xfb41, 0x3900, 0xf9c1, 0xf881, 0x3840,
		0x2800, 0xe8c1, 0xe981, 0x2940, 0xeb01, 0x2bc0, 0x2a80, 0xea41, 0xee01, 0x2ec0, 0x2f80, 0xef41, 0x2d00, 0xedc1, 0xec81, 0x2c40,
		0xe401, 0x24c0, 0x2580, 0xe541, 0x2700, 0xe7c1, 0xe681, 0x2640, 0x2200, 0xe2c1, 0xe381, 0x2340, 0xe101, 0x21c0, 0x2080, 0xe041,
		0xa001, 0x60c0, 0x6180, 0xa141, 0x6300, 0xa3c1, 0xa281, 0x6240, 0x6600, 0xa6c1, 0xa781, 0x6740, 0xa501, 0x65c0, 0x6480, 0xa441,
		0x6c00, 0xacc1, 0xad81, 0x6d40, 0xaf01, 0x6fc0, 0x6e80, 0xae41, 0xaa01, 0x6ac0, 0x6b80, 0xab41, 0x6900, 0xa9c1, 0xa881, 0x6840,
		0x7800, 0xb8c1, 0xb981, 0x7940, 0xbb01, 0x7bc0, 0x7a80, 0xba41, 0xbe01, 0x7ec0, 0x7f80, 0xbf41, 0x7d00, 0xbdc1, 0xbc81, 0x7c40,
		0xb401, 0x74c0, 0x7580, 0xb541, 0x7700, 0xb7c1, 0xb681, 0x7640, 0x7200, 0xb2c1, 0xb381, 0x7340, 0xb101, 0x71c0, 0x7080, 0xb041,
		0x5000, 0x90c1, 0x9181, 0x5140, 0x9301, 0x53c0, 0x5280, 0x9241, 0x9601, 0x56c0, 0x5780, 0x9741, 0x5500, 0x95c1, 0x9481, 0x5440,
		0x9c01, 0x5cc0, 0x5d80, 0x9d41, 0x5f00, 0x9fc1, 0x9e81, 0x5e40, 0x5a00, 0x9ac1, 0x9b81, 0x5b40, 0x9901, 0x59c0, 0x5880, 0x9841,
		0x8801, 0x48c0, 0x4980, 0x8941, 0x4b00, 0x8bc1, 0x8a81, 0x4a40, 0x4e00, 0x8ec1, 0x8f81, 0x4f40, 0x8d01, 0x4dc0, 0x4c80, 0x8c41,
		0x4400, 0x84c1, 0x8581, 0x4540, 0x8701, 0x47c0, 0x4680, 0x8641, 0x8201, 0x42c0, 0x4380, 0x8341, 0x4100, 0x81c1, 0x8081, 0x4040
	};

	Poco::UInt16 word = 0x00ff & static_cast<Poco::UInt16>(byte);
	Poco::UInt16 tmp = crc ^ word;
	crc = (crc >> 8) ^ crcTab[tmp & 0xff];

	return crc;
}


bool RTUPort::checkFrame(std::size_t size)
{
	poco_assert (size <= _receiveBuffer.size());

	if (size < 4) return false;

	Poco::MemoryInputStream istr(_receiveBuffer.begin(), size);
	Poco::BinaryReader binaryReader(istr, _byteOrder == RTU_BIG_ENDIAN ? Poco::BinaryReader::BIG_ENDIAN_BYTE_ORDER : Poco::BinaryReader::LITTLE_ENDIAN_BYTE_ORDER);

	Poco::UInt16 crc = 0xffff;
	for (int i = 0; i < size - 2; i++)
	{
		Poco::UInt8 byte;
		binaryReader >> byte;
		crc = updateCRC16(crc, byte);
	}
	Poco::UInt8 loCRC, hiCRC;
	binaryReader >> loCRC >> hiCRC;
	Poco::UInt16 receivedCRC = loCRC + (hiCRC << 8);
	return crc == receivedCRC;
}


} } } // namespace IoT::Modbus::RTU
